Braking distance

The car travels at an average speed of 12 km/h and detects an obstacle 10 m in front of it. At 1 m in front of the obstacle, it already runs 2 km/h. What is the braking distance? What is the required deceleration for a stop:

A) 1m
B) 1s?

Correct answer:

x =  12.96 m
a2 =  0.5556 m/s2

Step-by-step explanation:

v1=12 km/h m/s=12:3.6  m/s=3.33333 m/s s1=10 m s2=1 m v2=2 km/h m/s=2:3.6  m/s=0.55556 m/s  s=s1s2=101=9 m s = 21 a t2 at = (v1v2)  s = 21 (v1v2)   t  t=2 s/(v1v2)=2 9/(31095)=25162=6.48 s  a=tv1v2=2516231095=14586250.4287 m/s2  t1=v1/a=3.3333/0.4287=125972=7.776 s  x=21 a t12=21 0.4287 7.7762=25324 m=12.96 m
t2=2 s1/(v10)=2 10/(3100)=6 s a2=t2v1=63.3333=95 m/s2=0.5556 m/s2

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